The Hidden Danger of Improper Bathroom Fan Venting

Why Bathroom Fan Venting is Critical for Roof Health

During a recent roof inspection in Bergen County, we discovered a major ventilation issue—a bathroom fan duct blowing moisture directly into the attic instead of venting outside.

When bathroom moisture is trapped in the attic, it can lead to:

❌ Mold and mildew growth
❌ Excessive attic moisture buildup
❌ Premature roof decking deterioration
❌ Compromised insulation efficiency

Many homeowners are unaware of this issue until it’s too late—when they need a full roof replacement due to hidden moisture damage.

How We Discovered This Ventilation Problem

While replacing the roof decking on this home, we found that the bathroom fan duct was venting directly into the attic, saturating the wooden decking with moisture over time.

This excess moisture buildup likely contributed to the rotting of the decking, which required complete replacement.

Bathroom exhaust fans are supposed to vent steam and moisture outside, preventing attic humidity from weakening the roof structure.

The Right Way to Vent a Bathroom Fan

To prevent attic moisture problems, Mattsson Roofing is correcting this issue by installing a proper exhaust vent on the roof.

Steps to Fix the Problem:

1️⃣ Install a new 4-inch roof exhaust vent (brown vent).
2️⃣ Connect the existing bathroom fan duct to the exhaust vent.
3️⃣ Ensure proper moisture exhaust—so humid air gets vented outside, rather than into the attic.

With this fix, all bathroom moisture will exit the home correctly, protecting the roof decking from future water damage.

The Dangers of Trapped Moisture in Your Attic

When bathroom fans vent into the attic, the trapped moisture can cause long-term roofing problems, including:

❌ Rotting roof decking, leading to expensive repairs.
❌ Compromised attic insulation, reducing energy efficiency.
❌ Mold growth, which can spread and create health hazards.
❌ Shingle deterioration, as excess attic moisture weakens the roofing system.

This is why it’s essential to vent bathroom fans properly, ensuring moisture is expelled outside the home.

Protect Your Roof with Proper Ventilation: Contact Mattsson Roofing

If you suspect your bathroom fan is venting into your attic, or if you’re experiencing moisture buildup, mold, or roof damage, Mattsson Roofing can help.

We provide attic ventilation solutions, bathroom exhaust vent installations, and full roof repairs throughout Glen Rock, NJ and all of Bergen County.

📞 Call us today at 201.925.9709 or CLICK HERE to schedule a roof inspection!